Perineal Muscles

The perineal muscles are a group of skeletal muscles located in the superficial and deep layers of the perineum. They are involved in urogenital function, sexual activity, defecation, and support of pelvic viscera. These muscles are organized into two primary groups based on their location relative to the perineal membrane: superficial and deep perineal muscles. They differ between males and females but share a common structural and functional framework.

Structure

The perineal muscles are arranged around the urogenital and anal openings, forming slings and sphincters that control bodily functions and maintain pelvic integrity. They are innervated primarily by the **pudendal nerve (S2–S4)** and are supplied by branches of the **internal pudendal artery**.

Superficial Perineal Muscles

• Bulbospongiosus:
  • Males: Covers bulb of penis; aids in erection and expulsion of urine/semen
  • Females: Surrounds vaginal orifice; compresses greater vestibular glands
• Ischiocavernosus: Covers crura of penis or clitoris; helps maintain erection by compressing venous return
• Superficial transverse perineal muscle: Extends from ischial tuberosity to perineal body; stabilizes perineal body

Deep Perineal Muscles

• External urethral sphincter: Encircles urethra; allows voluntary urinary continence
• Deep transverse perineal muscle: Stabilizes perineal body and supports pelvic floor
• Compressor urethrae and sphincter urethrovaginalis (in females): Assist in urethral compression during continence

Anal Triangle Muscle

• External anal sphincter: Voluntary sphincter of the anal canal; maintains continence

Location

Perineal muscles are located in the perineum, divided between the urogenital and anal triangles. They are organized into two pouches separated by the perineal membrane:

Function

• Urinary continence: External urethral sphincter and compressor urethrae regulate urine flow
• Sexual function: Ischiocavernosus and bulbospongiosus aid in erection and ejaculation (males), and vaginal compression (females)
• Pelvic support: Transverse perineal muscles and sphincters stabilize the perineal body and support pelvic organs
• Fecal continence: External anal sphincter maintains anal closure

Clinical Significance

• Perineal tears: Common during childbirth; may involve superficial or deep muscles
• Pelvic floor dysfunction: Weakness or damage to perineal muscles may cause incontinence or organ prolapse
• Episiotomy: Involves cutting superficial perineal muscles to facilitate delivery